Ammunition feed and bolt lock mechanism for a closed breech rocket gun

ABSTRACT

A closed breech rocket gun has a rotatable feed shaft thereon for intermittently feeding a round of ammunition into the firing chamber as the shaft is rotated by means of a plunger rod movable outwardly of the gun receiver as the bolt retracts. A slidable cam plate interconnected with a gas cylinder and piston unit on the gun barrel retracts after the firing of each round and unlatches a bolt lock to permit the bolt to recoil, after which the bolt is again locked in place when the next round is fed into the firing chamber.

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United States Patent [1 1 1111 3,874,265

Kruzell Apr. 1, 1975 AMMUNITION FEED AND BOLT LOCK MECHANISM FOR A CLOSED BREECI-I ROCKET GUN FOREIGN PATENTS OR APPLICATIONS 881.370 4/1943 France 89/190 Primary E.\'aminerStephen C. Bentley Attorney, Agent. or FirmWatson, Cole. Grindle & Watson [57] ABSTRACT A closed breech rocket gun has a rotatable feed shaft thereon for intermittently feeding a round of ammunition into the firing chamber as the shaft is rotated by means of a plunger rod movable outwardly of the gun receiver as the bolt retracts. A slidable cam plate interconnected with a gas cylinder and piston unit on the gun barrel retracts after the firing of each round and unlatches a bolt lock to permit the bolt to recoil, after which the bolt is again locked in place when the next round is fed into the firing chamber.

8 Claims, 8 Drawing Figures characters \MMUNITION FEED ANI) BOLT LOCK \IECHANISM FOR A CLOSED BREECH ROCKET GUN l'his invention relates generally to closed breech guns. and more particularly to an automatic ammunition feed and bolt lock mechanistn therefor.

ln rocket guns in the type to which this invention relatcs. it is recognized that the breech closing mechanism thereof must be sufficiently reliable and efficient in effecti\ely closing the breech in a gas-tight manner to mold the dangerous rearward discharge of gases. Various locking mechanisms have been devised for maintaining the breech locked and sealed in its closed position and for releasing the bolt to permit a fresh round to be delivered into the firing chamber. An application Scr. No. 397.198 entitled Bolt Lock Mechanism for Closed Breech Gun-- has been filed by me of even date herewith as providing an improved and simplified lock mechanism for securely locking the bolt in its breech closing position. The present invention pertains to another version of such lock mechanism of equally simplified and improved arrangement. while at the same time providing for an automatic feed of an ammunition round each time the bolt retracts. A slidable cam plate is provided for effectively moving a bolt lock into its locked position during the forwardly proected position of the bolt. and for effectively unlatchmg the bolt lock during a retracted position ofthe cam plate. An outwardly movable plunger rod is provided in the path of mo\ ement of the bolt so as to be moved outwardly during contact by the bolt to thereby intermittently rotate a feed shaft which causes an ammunition unit to feed a round of ammunition to the firing chamber. [port projected movement of the bolt. the plunger rod moves inwardly and the bolt is locked in its forwardly projected sealed position as the cam plate pro ects forwardly under the action of a spring to latch the bolt lock element in place. This is the principal obcct of the present invention.

Other objects. advantages and novel features of the invention will become more apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings wherein:

lrlG. is a to plan cle\ational view in partial section of a portion of the rocket gun with the bolt locked in place in accordance with the invention:

l-IG. 2 is a side elevational view of the gun of FIG. 1 in partial section [tll\t.l"l along the line 22 thereof:

FIG. 3 is a slightly enlarged view similar to FIG. 1 showing the unlatched position of the bolt.

HG. 4 is an e\ en more slightly enlarged cross sectional \iew in elevation showing the retracted position of the bolt and the manner of moving the plunger rod outwardly.

FIG. 5 is a cross-sectional view showing the inwardly evtending plunger rod in its relation to a ratchet wheel taken along the line 55 of FIG 2;

FIG. 6 is a view similar to FIG. 5 showing the outward extension of the plunger rod;

FIG. 7 is a perspective view of the feed wheel which effects rotation of the feed shaft; and

FIG. 8 is a sectional view taken along line 88 of FIG. 2 showing the ammunition feeding unit.

lurnmg now to the drawings wherein like reference refer to like and corresponding parts throughout the several views. top plan and side elevational views of a part of the rocket gun is shown respectively in FIGS. 1 and 2 with those elements such as the gun stock. firing pin and trigger being omitted for the sake of clarity. The rocket gun comprises a barrel l0 having a bore 11 extending therethrough which communicates at its rearward end with a receiver l2 through a breech opening 13. The receiver has a bolt well 14 and defines at its forward end a conical sealing surface 15 surrounding the breech opening.

The breech closure herein is in the form of a bolt 16 of generally cylindrical cross-section and dimension throughout the major portion of its length corresponding to that of bolt well 14 which is also normally of uniform cross-sectional shape throughout its length. Bolt 16 is guided within the well for longitudinal sliding movement between its forwardly projected breech closing and sealing or firing position. as shown in FlGs. l and 2. and its fully retracted position as shown in phantom outline in FIG. I and in solid outline in FIG. 4. The forward end of the bolt is provided with a forwardly converging conical sealing surface 18 tapered at an angle similar to that of sealing surface 15 so that. in the forwardly projected position of the bolt. the con tacting sealing surfaces 15 and 18 provide a gastight seal rearwardly of firing chamber I9 and of breech opening 13 so as to prevent the rearward escape of gases incident to the firing of the weapon.

A bolt lock element in the form of a plate 21 is mounted within a cutout portion 22 at the outer stlrfacc of the receiver wall for inward and outward pivotal movement about a pivot pin 23. Plate 2] is resiliently urged inwardly by means of a leaf spring 24 mounted at one end as at 25 to the wall of the receiver. Also, plate 21 is provided with a bolt lock retracting pin 26 near its forward end by means of which the plate is moved against the action of spring 24 into its outward position in a manner to be hereinafter described. The bolt is locked in its forwardly projected position of FIGs. l and 2 as the forward end wall 27 of plate 21 abuts against a bolt operating pin 28 mounted on the bolt.

A cam plate 29 is mounted on the receiver for sliding movement within an elongated groove 3I (see FIG. 5 the cam plate having an elongated slot 32 therein and a slightly enlarged opening 33 at the rearward end of the slot defining an abutment wall 34. Retracting pin 26 of the bolt lock plate extends through this opening 33 while the bolt is in its forwardly locked position of FIGS. 1 and 2. The cam plate is also provided with a slightly elongated slot 35 through which bolt operating pin 28 extends at all times. An elongated slot 36 is provided within the wall of the receiver and it communicates with slot 35 of the cam plate so that pin 28 may also extend through slot 36 as the bolt is moved between its forwardly projected and retracted positions. The bolt is unlocked from its forwardly locked and sealed positions of FIGS. 1 and 2 at the commencement of rearward movement of the cam plate. During such rearward movement, abutment wall 34 contacts pin 26 of the bolt lock plate and, as pin 26 slides along this wall disposed at an angle with respect to the longitudinal axis of the bolt. plate 21 is caused to move outwardly as shown in FIG. 3. Continued movement of the cam plate causes plate 21 to be retained in its outwardly moved position as pin 26 is guided along elongated slot 32. Also, bolt 16 moves rearwardly along with the cam plate through the interengagement of bolt operation pin 28 and slot 35.

The cam plate is him ed rearwardly for unlatching the bolt lock plate in timed relation to the li ring of a round of ammunition Such is effected by means of gas cylinder and piston unit shown in FIG. 2 as comprising a piston 37 disposed for longitudinal rearward movement in a cylinder 38. similarly as in one of my prior LS. Pat. No. 3.227.045. gas inlet passage 39 of a gas cylinder 38 is located at a suitable position along the length of the barrel and near its discharge end to admit pressur ized gases from the rearward end of projectile P as it moves along the inlet end of this passage. The position of the inlet end of passage 39 is therefore such that piston 37 will he actuated to move the cam plate rearwardly to disengage plate 2] from bolt [6 at a time when there is sufficient gas pressure remaining in the barrel to force the bolt rearwardly.

Rearward movement of piston 37 is transmitted to the cam plate as its piston rod 41 pushes against the forward end of a release rod 42 mounted at the forward end of the cam plate. The release rod slides within a forward bearing wall 43 of the receiver within an opening 44. and the cam plate is urged in a forward direction by means of a spring 45 coiled about the release rod under compression between bearing wall 43 and a suitable stop (not shown) provided on the rod.

Release rod 42 is also adapted for manual actuation as by means of a bolt release plunger 46 slidably guided through bearing 47 provided in gas cylinder 38. The rearward end of plunger 46 is guided for abutting en gagement with abutment 48 mounted on the release rod to transmit rearward movement to the rod. Plunger 46 is resiliently urged forwardly by means of a compression spring 49. Also. plunger 46 is normally disengaged from release rod 42 so as to avoid any interference with the actuation of the rod by the aforedescribed automatic means.

In addition to the bolt lock and release mechanism described above. the invention includes an automatic ammunition feed arrangement for intermittently feed ing ammunition into the bolt well. Such an arrangement includes a feed wheel plunger 4] slidably mounted within a support 52 attached to the receiver near the rearward end thereof. Plunger 51 is resiliently urged into the path of movement of the bolt by means of a coil spring 53 surrounding the shaft 54 of the plunger and being suitably mounted within support 52 as shown in FIGS. I and 4. The plunger is provided with a sloping end wall 55 for contacting engagement with the similarly sloping end wall 56 at the rearward end of bolt 16. Accordingly. rearward movement of the bolt to its fully retracted position of FIG. 4 mo\ es plunger 51 into its fully retracted position outwardly of the receiver as sloping end wall 55 moves beyond sloping end wall 56 of the bolt.

A feed shaft 57 is mounted on the receiver for rotational movement by means of bearings 58. A feed ratchet wheel 59 is mounted near the rearward end of shaft 57 for rotation therewith. As seen most clearly in FIGS. 5. 6 and 7. this ratchet wheel is provided with ratchet teeth 6| equally spaced from one another and extending outwardly of a side wall of the w heel. Each of the teeth 6| has a pair of abutment walls 62. 63 at right angles. and an outer surface 64 sloping outwardly from the side wall surface toward wall 62. Equally spaced detents 66 are also provided along the outer pe (ill riphery of the ratchet wheel in alignment with the end of each tooth 6| opposite wall 62. A detent ball 67 extends partially outwardly of a cylindrical opening 68 provided in support 52 and rests within one of the detents to act as a stop during partial rotation of wheel 59. The ball is urged into the detent by a spring 69. the spring force of which is adjusted by means of a detent adjustment screw 7 I Plunger 5] is provided with an outwardly extending thin plate-like finger element 72 disposed adjacent one of the abutment walls 62 of the ratchet teeth in the extended position ofthe plunger shown in FIG. 5. Therefore. as bolt 16 retracts and causes plunger 5] to retract within its housing 52. finger 72 contacts abutment wall 62 and causes wheel 59 to rotate 90 in the direction of the arrow to its position shown in FIG. 6 wherein finger 72 is not in abutment with wall 63 of the ratchet tooth. When cam plate 29 and bolt 16 return to their forwardly projection positions. plunger 51 is permitted to again extend inwardly of the receiver bolt well as in FIG. I whereupon finger 71 slides along sloping surface 64 of the adjacent tooth as shown in phantom outline in l-IG. 2. Interference is therefore effectively a\ oidcd between the plunger finger and the teeth during the evtended return movement of the plunger.

Feed sprockets 73 are also mounted on feed shaft 57 for rotation therewith. each of these sprockets having teeth 74 for interengagement with aligned feed holes 75 provided in a feed belt 76 as shown in FIG. 8. Spaced ammunition clips 77 are mounted on the belt which is guided for mmement in the direction of the arrow of FIG. 8 within a magazine housing 78 by means of guide rolls 79 hearing against the undersurface of the belt. and guide rolls 81 hearing against the top surface of the belt.

It should be also pointed out that a cover plate 82 is secured in place over the top of the cam plate as by means of screw fasteners on bearing wall 43. end wall 83 and side walls 84 of the receiver. Also. an end cap 85 is provided at the rearward end of the receiver.

In brielIy' summari7ing the overall operation of the closed breech rocket gun of the invention. bolt 16 is locked in its forwardly projected sealed position of FIGS. I and 2 as leaf spring 24 urges bolt lock plate 2] inwardly so that its forward end wall 27 abuts against bolt operating pin 28 to maintain the bolt in a locked position. Upon the firing of a round of ammunition. the gases emanating from behind projectile P moving past gas inlet passage 39 cause piston 37 of the gas cylinder and piston unit to be moved rearwardly so that piston rod 4] causes release rod 42 to also move rearwardly and carry along with it cam plate 29. At the commencement of this rearward movement of the cam plate as shown in FIG. 3. sloping abutment wall 34 thereof causes plate 21 to be shifted outwardly as its retracting pin 26 slides along wall 34 within opening 33. Continued movement of the cam plate permits the bolt to recoil to its retracted position and the cam plate is carried along with the bolt through the interengagement between bolt operating pin 28 thereof and slot 35 of the cam plate. Pin 28 is guided along slot 36 of the re' ceiver. and pin 26 is guided along slot 32 of the cam plate during this retractive movement. When sloping end wall 36 of the bolt contacts sloping end wall 55 of plunger 5]. the plunger is moved inwardly of its housing 52 and outwardly of the receiver and into a fully retracted position of the plunger as end wall 56 moves therebeyond as in l-l(i. 4. This retractive movement of the plunger effects an intermittent feed of a single round of ammunition into the firing chamber as finger element 72 abuts successi\ely against walls 62 and 63 ofone of the ratchet teeth. The ratchet wheel is thereof rotated clockwise throughout 90 when viewing FIG. 6 as limited by detent hall 67 moving along the periphery of the ratchet wheel from one of its detents shown in Fl(i. 5 to an adjacent one as shown in FIG. 6. This 90 rotation of the ratchet wheel causes feeder shaft 57 to be likewise rotated throughout 90 to therefore rotate feed sprockets 73 which move belt 76 a distance equal to the spacing between clips 77. The center clip in FIG. 8 is \hUWI] in alignment with the firing chamber and the remaining clips behind it also contain a projectile P for subsequent loading (lips 77 ahead of the center clip lonly one shown) are empty after its projectile P has been loaded and fired.

-\fter loading a round into the bolt well. coil spring 45 urges the cam plate from its retracted position into a forward direction of movement. and engagement between pin 28 on the bolt and slot 35 on the cam plate causes the bolt to be Iikc\\'isc moved toward its forward projected position. During such movement. pin 28 is guided by elongated slot 36 and pin 26 is guided along elongated slot 32. Continued forward movement of cam plate from its position of FIG. 3 causes bolt lock plate Zl to again be pivoted inwardly as its pin 26 moves into slot 33 under the force of leaf spring 24 so that its forward end wall 27 again abuts against bolt operating pin 28 to maintain the bolt locked in its forward pro ected position. The projectile P has therefore been moved into firing chamber 19 in readiness for firing after which the cycle of operation as set forth above is repeated.

Obviously. many modifications and variations of the invention are made possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims. the invention may be practiced otherwise than as specifically described.

What is claimed is:

1. In a closed breech rocket gun including a barrel ha\ing a bore extending therethrough and communieating at its rearward end with a receiver through a breech opening. said receiver defining a sealing surface around said breech opening. a bolt guided for projection and retraction movement in said receiver respectively toward and away from said breech opening and formed with a sealing surface for flush sealing engagement with said receiver sealing surface in the forwardly projected position of said bolt. a bolt operating pin on said bolt. a bolt lock element resiliently mounted on said receiver for movement inwardly of said receiver into locking engagement with said bolt operating pin and outwardly of said receiver out of engagement with said bolt operating pin. a cam plate slidably guided on said receiver for movement parallel to said bolt movement and ha\ing a cam surface for engagement with said bolt lock element for moving it outwardly of said receiver when said cant plate retracts. said cam plate being operatively connected with said bolt for movement thereof. a gas cylinder and piston unit communicating with said barrel for the reception of pressurized gas therefrom for actuating said unit, linkage means operathely interconnecting said unit with said cam plate for retracting same incident to the firing of a round of ammunition through said barrel. resilient means urging said cam plate to its projected position. a plunger rod resiliently mounted on said receiver for transverse movement into and out of the path of movement ofsaid bolt. a feed shaft rotatably mounted on said receiver and parallel thereto. an ammdnition feed unit in engagement with said shaft for feeding a round of ammunition into said firing chamber upon rotation of said shaft. said plunger rod engaging said bolt each time said bolt retracts to thereby cause said rod to engage said shaft for intermittent rotation thereof each time said rod mo\es outwardly of the path of movement of said bolt. whereby said bolt lock element is unlatehed as said cam plate retracts. and a round of ammunition is fed into said firing chamber as said bolt retracts and moves said plunger rod outwardly so as to rotate said shaft.

2. The closed breech g'un according to claim I wherein said cam plate has an elongated cam slot defining said cam surface. and said bolt lock element having a pin thereon extending into said slot for relative sliding movement with respect thereto during the retracted movement of said cam plate. and said bolt lock element being moved outwardly as said pin engages with said catn surface during the retracted movement of said cam plate.

3. The closed breech gun according to claim 2 wherein said cam plate is provided with a slightly elongated opening. said bolt operating pin on said bolt extending into said opening for movement by said cam plate into a forwardly projected position as said cam plate is urged by said resilient means into its projected position.

4. In a closed breech rocket gun including a barral having a bore extending therethrough and communieating at its rearward end with a receiver through a breech opening. said receiver defining a sealing surface around said breech opening. a bolt guided for projection and retraction movement in said receiver respec' tively toward and away from said breech opening and formed with a sealing surface for flush sealing engagement with said receiver sealing surface in the forwardly projected position of said bolt, a bolt lock element resiliently mounted on said receiver for movement inwardly of said receiver into locking engagement with said bolt. and outwardly of said receiver out of engagement with said bolt. a cam plate slidably guided on said receiver for movement parallel to said bolt movement and having a cam surface for engagement with said bolt lock element for moving it outwardly of said receiver when said cam plate retracts. whereby said bolt lock element is unlatched as said cam plate retracts. a gas cylinder and piston unit communicating with said barrel for the reception of pressurized gas therefrom for actuating said unit. linkage means operatively interconnecting said unit with said cam plate for retracting same incident to the firing of a round of ammunition through said barrel. resilient means urging said cam plate to its projected position. a plunger rod resiliently mounted on said receiver for transverse movement into and out of the path of movement of said bolt, said plunger rod also being disposed for rotational movement about its principal axis, a feed shaft rotatably mounted on said receiver and parallel thereto. an ammunition feed unit in engagement with said shaft for feeding a round of ammunition into said firing chamber upon rotation of said shaft, said plunger rod engaging said bolt each time said bolt retracts to thereby cause said rod to mow outwardly of the path of movement of said bolt. said rod engaging said shaft for intermittent rotation thereof each time said rod mo\ es outwardh of the path of movement of said bolt. said shaft causing said rod to rotate about its said axis during movement thereof back into the path of movement of said bolt. whereb v a round of ammunition is fed into said firing chamber as said bolt retracts and moves said plunger rod outwardly so as to rotate said shaft.

5. The closed breech gun according to claim 4 wherein a ratchet wheel is mounted on said shaft for rotation therewith. said plunger rod engaging a tooth of said ratchet wheel for rotation of said shaft each time said plunger rod is moved outwardl of said receiver 6. The closed breech gun according to claim 5 wherein the teeth of said ratchet wheel extend outwardly of one side thereof, each said teeth of said ratchet wheel ha\ ing flat abutment surfaces and a sloping surface. said plunger rod having a finger element thereon in engagement with the abutment surfaces of one of said teeth for rotating said ratchet wheel during outward movement of said plunger. said sloping surfaces permitting said finger element to bypass said teeth and causing said rod to rotate during inward movement thereof.

7. The closed breech gun according to claim 4 wherein said ammunition feed unit includes a feed sprocket mounted on said shaft for rotation therewith, and a feed band having ammunition clips thereon. said feed band being in engagement with said feed sprocket for intermittent feeding of a round of ammunition into said firing chamber upon rotation of said shaft.

8. The closed breech gun according to claim 4 wherein the rearward end of said bolt and the inner end of said plunger rod respectively have mating sloping surfaces to facilitate outward movement of said plunger rod upon contact between said surfaces during the retractcd mo\ement of said bolt. 

1. In a closed breech rocket gun including a barrel having a bore extending therethrough and communicating at its rearward end with a receiver through a breech opening, said receiver defining a sealing surface around said breech opening, a bolt guided for projection and retraction movement in said receiver respectively toward and away from said breech opening and formed with a sealing surface for flush sealing engagement with said receiver sealing surface in the forwardly projected position of said bolt, a bolt operating pin on said bolt, a bolt lock element resiliently mounted on said receiver for movement inwardly of said receiver into locking engagement with said bolt operating pin and outwardly of said receiver out of engagement with said bolt operating pin, a cam plate slidably guided on said receiver for movement parallel to said bolt movement and having a cam surface for engagement with said bolt lock element for moving it outwardly of said receiver when said cam plate retracts, said cam plate being operatively connected with said bolt for movement thereof, a gas cylinder and piston unit communicating with said barrel for the reception of pressurized gas therefrom for actuating said unit, linkage means operatively interconnecting said unit with said cam plate for retracting same incident to the firing of a round of ammunition through said barrel, resilient means urging said cam plate to its projected position, a plunger rod resiliently mounted on said receiver for transverse movement into and out of the path of movement of said bolt, a feed shaft rotatably mounted on said receiver and parallel thereto, an ammunition feed unit in engagement with said shaft for feeding a round of ammunition into said firing chamber upon rotation of said shaft, said plunger rod engaging said bolt each time said bolt retracts to thereby cause said rod to engage said shaft for intermittent rotation thereof each time said rod moves outwardly of the path of movement of said bolt, whereby said bolt lock element is unlatched as said cam plate retracts, and a round of ammunition is fed into said firing chamber as said bolt retracts and moves said plunger rod outwardly so as to rotate said shaft.
 2. The closed breech gun according to claim 1 wherein said cam plate has an elongated cam slot defining said cam surface, and said bolt lock element having a pin thereon extending into said slot for relative sliding movement with respect thereto during the retracted movement of said cam plate, and said bolt lock element being moved outwardly as said pin engages with said cam surface during the retracted movement of said cam plate.
 3. The closed breech gun according to claim 2 wherein said cam plate is provided with a slightly elongated opening, said bolt operating pin on said bolt extending into said opening for movement by Said cam plate into a forwardly projected position as said cam plate is urged by said resilient means into its projected position.
 4. In a closed breech rocket gun including a barral having a bore extending therethrough and communicating at its rearward end with a receiver through a breech opening, said receiver defining a sealing surface around said breech opening, a bolt guided for projection and retraction movement in said receiver respectively toward and away from said breech opening and formed with a sealing surface for flush sealing engagement with said receiver sealing surface in the forwardly projected position of said bolt, a bolt lock element resiliently mounted on said receiver for movement inwardly of said receiver into locking engagement with said bolt, and outwardly of said receiver out of engagement with said bolt, a cam plate slidably guided on said receiver for movement parallel to said bolt movement and having a cam surface for engagement with said bolt lock element for moving it outwardly of said receiver when said cam plate retracts, whereby said bolt lock element is unlatched as said cam plate retracts, a gas cylinder and piston unit communicating with said barrel for the reception of pressurized gas therefrom for actuating said unit, linkage means operatively interconnecting said unit with said cam plate for retracting same incident to the firing of a round of ammunition through said barrel, resilient means urging said cam plate to its projected position, a plunger rod resiliently mounted on said receiver for transverse movement into and out of the path of movement of said bolt, said plunger rod also being disposed for rotational movement about its principal axis, a feed shaft rotatably mounted on said receiver and parallel thereto, an ammunition feed unit in engagement with said shaft for feeding a round of ammunition into said firing chamber upon rotation of said shaft, said plunger rod engaging said bolt each time said bolt retracts to thereby cause said rod to move outwardly of the path of movement of said bolt, said rod engaging said shaft for intermittent rotation thereof each time said rod moves outwardly of the path of movement of said bolt, said shaft causing said rod to rotate about its said axis during movement thereof back into the path of movement of said bolt, whereby a round of ammunition is fed into said firing chamber as said bolt retracts and moves said plunger rod outwardly so as to rotate said shaft.
 5. The closed breech gun according to claim 4 wherein a ratchet wheel is mounted on said shaft for rotation therewith, said plunger rod engaging a tooth of said ratchet wheel for rotation of said shaft each time said plunger rod is moved outwardly of said receiver.
 6. The closed breech gun according to claim 5 wherein the teeth of said ratchet wheel extend outwardly of one side thereof, each said teeth of said ratchet wheel having flat abutment surfaces and a sloping surface, said plunger rod having a finger element thereon in engagement with the abutment surfaces of one of said teeth for rotating said ratchet wheel during outward movement of said plunger, said sloping surfaces permitting said finger element to bypass said teeth and causing said rod to rotate during inward movement thereof.
 7. The closed breech gun according to claim 4 wherein said ammunition feed unit includes a feed sprocket mounted on said shaft for rotation therewith, and a feed band having ammunition clips thereon, said feed band being in engagement with said feed sprocket for intermittent feeding of a round of ammunition into said firing chamber upon rotation of said shaft.
 8. The closed breech gun according to claim 4 wherein the rearward end of said bolt and the inner end of said plunger rod respectively have mating sloping surfaces to facilitate outward movement of said plunger rod upon contact between said surfaces during the retracted movement of said bolt. 